Computer users who are using large displays such as a 20", 21", 23" or 30" monitor or LCD (especially one that is a widescreen) may want to split that large display into two different displays vertically or horizontally to be more productive and be able to work or view two things at once. In order for a user to do this we suggest installing a third-party software program designed to do this. Below are some programs that can help users with doing this.
SplitView

http://www.splitview.com/download.htm
SplitView is a great program that splits windows on your screen and allows you to manage and display split windows. The program does not necessarily create two separate displays. But does give the user a much easier way to split their windows and move them on screen. Once installed two additional buttons will be added to each window at the top left that can be clicked to split the window.
GridMode

http://jgpaiva.donationcoders.com/gridmove.html
GridMode is another excellent program and a free alternative that enables users to split their screen into grids. Once split up the user can drag windows into the grids and manage windows different ways. To drag to a grid move the window to one of the edges of the screen.
nVidia Grids

http://www.nvidia.com
Users with nVidia video cards installed with 3.0 desktop manager and later can use the nVidia Grids to break up their windows. To do this right-click on the nVidia settings, open nVidia Desktop Manager, and click Edit Display Grids. Once you've edited the display grids you can move windows to the grids by holding down Alt and dragging the window to a grid or right-click on the window bar, click nVidia Options, and Maximize to grid.

by: Nguyen Viet Cuong :)